1. Field of the Invention
The present invention relates to a signal regulator module, and more particularly, to a signal regulator module capable of adjusting driving signals outputted by a driving circuit to light sources of a display panel.
2. Description of the Prior Art
A liquid crystal display (LCD) device can provide rich images by controlling liquid crystal pixels of a display panel using transistors arranged in matrix, together with appropriate electronic components such as capacitors, switches, and pads. Due to thin appearances, low power consumption, and low radiation, LCD devices have gradually replaced traditional cathode ray tube (CRT) displays and are widely used in portable electronic devices such as notebook computers, personal digital assistants (PDA) and digital cameras.
Generally speaking, an LCD device includes an LCD panel and a backlight module disposed at the lower or lateral sides of the LCD panel. A light source and various optical devices (such as diffusion plates and prisms) are used for providing high-intensity and uniform light for the LCD panel. By controlling the luminance of liquid crystal pixels, the LCD device can display corresponding images. Being the key device in an LCD device, the backlight module including a light source and an optical film, is capable of providing uniform light. Based on the location of the light source, backlight modules can be categorized into direct-type and edge-type backlight modules. In a direct-type backlight module, light is generated directly beneath the LCD panel. In an edge-type backlight module, light is generated near the lateral sides of the LCD panel. Since light of higher-intensity is provided when generated directly beneath the LCD panel, the direct-type backlight module can be applied in high-brightness or large-size LCD panels, such as in flat panel television sets.
Referring to FIG. 1. FIG. 1 is a diagram of a prior art LCD backlight module driving circuit 10. The LCD backlight module driving circuit 10 includes a plurality of transformers TR1-TRn for respectively driving lamps L1-Ln. In the prior art LCD backlight module driving circuit 10, each lamp is driven by a transformer. With increasing demands in large-size applications, the panel size becomes larger and the number of lamps used in the LCD device also increases accordingly. Therefore, the prior art LCD backlight module driving circuit 10 requires more transformers, which largely raises manufacturing costs.
Referring to FIG. 2. FIG. 2 is a diagram of another prior art LCD backlight module driving circuit 20. The LCD backlight module driving circuit 20 includes a transformer TR for simultaneously driving lamps L1-Ln. IL1-ILn represent the currents passing through the lamps L1-Ln, respectively. In the prior art LCD backlight module driving circuit 20, a transformer is used for driving multiple lamps. Therefore, in large-size applications, the number of the transformers and driving switches can be reduced, thereby cutting manufacturing costs. However, since the lamps L1-Ln may have different characteristics, the currents IL1-ILn passing through the lamps L1-Ln may also vary. Each lamp can thus provide distinct luminance, which lowers the uniformity of the backlight module and influences the display quality of the LCD device.
Referring to FIG. 3. FIG. 3 is a diagram of another prior art LCD backlight module driving circuit 30. In the LCD backlight module driving circuit 30, a balance circuit is used for improving the current uniformity when driving multiple lamps, and only two lamps are depicted in FIG. 3 for ease of illustration. The LCD backlight module driving circuit 30 includes a transformer TR and a balance circuit 32 for driving lamps L1 and L2. IL1 and IL2 represent the currents passing through the lamps L1 and L2, respectively. The balance circuit 32 includes active components such as transistors Qp and Qn, diodes Dp and Dn, comparator 34, and impedance device Cx. Since the balance circuit 32 adopts an active design, it generates a feedback signal V1 pertaining to the current IL1 and a feedback signal V2 pertaining to the current IL2. The comparator 34 can compare the feedback signals V1 and V2, output a corresponding switch voltage signal Vsw based on the difference between the feedback signals V1 and V2, and send the switch voltage signal Vsw to the gates of the transistors Qp and Qn. In response to the switch voltage signal Vsw, the transistors Qp and Qn are turned on and turned off for regulating the current IL2, so that the current IL2 can approach the current IL1.
In the prior art LCD backlight module driving circuit 30 having an active design, current adjustment is performed based on the actual feedback current. Under environmental influences, lamp currents can still be regulated to nominal values. However, the transistors Qp and Qn of the LCD backlight module driving circuit 30 operate in the switching region in which the current waveforms of the lamps can have asymmetrical positive/negative half periods due to characteristic variations in the transistors (such as the turn-on and turn-off speeds). Unless a direct current (DC) signal is applied continually, the current waveforms of the lamps can deform, which shortens the life of the lamps. Although the feedback signal V2 pertaining to the actual current IL2 of the lamp L2 is used in the LCD backlight module driving circuit 30, the comparator 34, merely capable of outputting logic signals having high/low levels, cannot reveal the accurate difference between the currents IL1 and IL2. Due to slow response speed of the comparator 34, it takes a long time for the LCD backlight module driving circuit 30 to reach equilibrium. Also, since the balance circuit 32 can only be used at the low-voltage end of the lamps, the LCD backlight module driving circuit 30 cannot be applied to large-size panels having a dual-side driving structure.